1. Field of the Invention
The present invention relates to pulsed laser systems, and more particularly to solid state laser systems for generating high power laser pulses at relatively high repetition rates with good beam quality.
2. Description of Related Art
High powered pulsed lasers that generate high quality output beams are being used in a variety of applications. A typical prior art system is offered by Spectra-Physics Lasers, Inc., under model number GCR-4-50. The GCR-4-50 is typical of the higher repetition rate systems. It includes two neodymium doped YAG rods in series within a resonant cavity. The two YAG rods are mounted in respective dual-ellipse pump cavities having two flashlamps each. The system is operated at about 50 Hz by simultaneously pumping all four flashlamps. The input pulse energy in each of the two pump chambers at 50 Hz is typically around 50 lamp joules, or 5 kW input (2.times.50 Hz.times.50 joules). Specified output energy is 700 millijoules per pulse for 35 W average output power with 50 pulses per second, at 1064 nm in a high quality 70% Gaussian fit beam profile. Total laser output power to lamp input power efficiency is greater than 0.65% near 0.70%.
Many applications require a repetition rate of higher than 50 Hz. However, as the repetition rate for pumping the flashlamps increases, the average power and beam quality decrease dramatically. For instance, in an experiment using a GCR-4-50 at 100 Hz, the input pulse energy in each of the two pump chambers at 100 Hz was halved to 25 lamp joules thus maintaining 5 kW input power (2.times.100 Hz.times.25 joules). Average output power in this 100 Hz configuration fell off about 70% from the 50 Hz system. In a GCR-4-50 system configured for 700 millijoules per pulse at 50 Hz, the 100 Hz pumping at 5 kW input power would therefore yield about 105 millijoules per pulse for 10.5 W average output power, and output power to lamp input power efficiency of about 0.21%.
Thus, prior art systems have been unable to achieve high powers with consistent beam quality with higher repetition rates. Accordingly, it is desirable to provide a laser system design capable of operating at higher pulse rates, while maintaining high efficiency and high quality output beams.